Fluid delivery device with conformable ullage

ABSTRACT

An apparatus for accurately infusing fluids into a patient at specific rates over an extended period of time. The apparatus is of a low profile, laminate or layered construction having a stored energy source in the form of a distendable membrane, which, in cooperation with the base of the apparatus, defines one or more fluid reservoirs, each having a fluid inlet and a fluid outlet. The apparatus further includes, a novel conformable ullage made of yieldable materials. The conformable ullage uniquely conforms to the geometry of elastomeric membrane as the membrane returns to its less distended configuration and in so doing can move between a central chamber and a toroidal chamber formed in the cover of the apparatus. This arrangement will satisfy even the most stringent medicament delivery tolerance requirements and will elegantly overcome the limitations of materials selection encountered in devices embodying solely a rigid ullage construction. Additionally, the infusion cannula of the apparatus is connected to the base in a novel manner which permits expeditious subdermal delivery to the patient via a cannula which extends generally perpendicularly relative to the base.

This application is related to application Ser. No. 08/451,520 filed May26, 1995 now U.S. Pat. No. 5,656,032 and is also related to aContinuation-In-Part application Ser. No. 08/540,914 filed on even dateherewith.

This application is related to application Ser. No. 08/451,520 filed May26, 1995 now U.S. Pat. No. 5,656,032 and is also related to aContinuation-In-Part application Ser. No. 08/540,914 filed on even dateherewith.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to fluid delivery devices. Moreparticularly, the invention concerns an improved apparatus for infusingmedicinal agents into an ambulatory patient at specific rates overextended periods of time.

2. Discussion of the Invention

A number of different types of liquid dispensers for dispensingmedicaments to ambulatory patients have been suggested. Many of thedevices seek either to improve or to replace the traditional hypodermicsyringe which has been the standard for delivery of liquid medicamentssuch as insulin solution.

Those patients that require frequent injections of the same or differentamounts of medicament, find the use of the hypodermic syringe bothinconvenient and unpleasant. Further, for each injection, it isnecessary to first draw the injection dose into the syringe, then checkthe dose and, after making certain that all air has been expelled fromthe syringe, finally, inject the dose. This cumbersome and tediousprocedure creates an unacceptable probability of debilitatingcomplications, particularly for the elderly and the infirm.

One example of the urgent need for an improved liquid delivery devicefor ambulatory patients can be found in the stringent therapeuticregimens used by insulin-dependent diabetics. The therapeutic objectivefor diabetics is to consistently maintain blood glucose levels within anormal range. Conventional therapy involves injecting insulin by syringeseveral times a day, often coinciding with meals. The dose must becalculated based on glucose levels present in the blood. If the dosageis off, the bolus administered may lead to acute levels of eitherglucose or insulin resulting in complications, including unconsciousnessor coma. Over time, high concentrations of glucose in the blood can alsolead to a variety of chronic health problems, such as vision loss,kidney failure, heart disease, nerve damage, and amputations.

A recently completed study sponsored by the National Institutes ofHealth (NIH) investigated the effects of different therapeutic regimenson the health outcomes of insulin-dependent diabetics. This studyrevealed some distinct advantages in the adoption of certain therapeuticregimens. Intensive therapy that involved intensive blood glucosemonitoring and more frequent administration of insulin by conventionalmeans, for example, syringes, throughout the day saw dramatic decreasesin the incidence of debilitating complications.

The NIH study also raises the question of practicality and patientadherence to an intensive therapy regimen. A bona fide improvement ininsulin therapy management must focus on the facilitation of patientcomfort and convenience as well as dosage and administration schemes.Basal rate delivery of insulin by means of a convenient and reliabledelivery device over an extended period of time represents one means ofimproving insulin management. Basal rate delivery involves the deliveryof very small volumes of fluid (for example, 0.5-3 mL. depending on bodymass) over comparatively long periods of time (18-24) hours). As will beappreciated from the discussion which follows, the apparatus of thepresent invention is uniquely suited to provide precise fluid deliverymanagement at a low cost in those cases where a variety of precisedosage schemes are of utmost importance.

With regard to the prior art, one of the most versatile and unique fluiddelivery apparatus developed in recent years is that developed by one ofthe present inventors and described in U.S. Pat. No. 5,205,820. Thecomponents of this novel fluid delivery apparatus generally include: abase assembly, an elastomeric membrane serving as a stored energy means,fluid flow channels for filling and delivery, flow control means, acover, and an ullage which comprises a part of the base assembly. Theullage in these devices, that is the amount of the fluid reservoir orchamber that is not filled by fluid, is provided in the form of asemi-rigid structure having flow channels leading from the top of thestructure through the base to inlet or outlet ports of the device. Sincethe inventions described herein represent improvements over thosedescribed in U.S. Pat. No. 5,205,820 this patent is hereby incorporatedby reference as though fully set forth herein.

In the rigid ullage configuration described in U.S. Pat. No. 5,205,820,wherein the ullage means is more fully described, the stored energymeans of the device must be superimposed over the ullage to form thefluid-containing portion of the reservoir from which fluids are expelledat a controlled rate by the elastomeric membrane of the stored energymeans tending to return to a less distended configuration in thedirection toward the ullage. With these constructions, the stored energymembrane is typically used at high extensions over a significantly largeportion of the pressure-deformation curve.

For good performance, the elastomeric membrane materials selected forconstruction of the stored energy membrane must have good memorycharacteristics under conditions of high extension; good resistance tochemical and radiological degradation; and appropriate gas permeationcharacteristics depending upon the end application to be made of thedevice. Once an elastomeric membrane material is chosen that willoptimally meet the desired performance requirements, there still remaincertain limitations to the level of refinement of the deliverytolerances that can be achieved using the rigid ullage configuration.These result primarily from the inability of the rigid ullage to conformto the shape of the elastomeric membrane near the end of the deliveryperiod. This nonconformity can lead to extended delivery rate tail-offand higher residual problems when extremely accurate delivery isrequired. For example, when larger volumes of fluid are to be delivered,the tail-off volume represents a smaller portion of the fluid amountdelivered and therefore exhibits must less effect on the total fluiddelivery profile, but in very small dosages, the tail-off volume becomesa larger portion of the total volume. This sometimes places severephysical limits on the range of delivery profiles that may easily beaccommodated using the rigid ullage configuration.

As will be better appreciated from the discussion which follows, theapparatus of the present invention provides an elongated, unique,disposable fluid dispenser of simple but highly reliable constructionthat may be adapted to a wide variety of end use applications. Aparticularly important aspect of the improved apparatus is theincorporation of conformable ullages made of yieldable materials whichuniquely conform to the shape of the stored energy membrane as themembrane distends and then returns to a less distended configuration.The conformable ullages are uniquely contained within contiguouschambers and are free to move from one chamber to another as the storedenergy membrane distends and then returns to a less distendedconfiguration. This novel construction, which permits the overall heightof the device to be minimized, will satisfy even the most stringentdelivery tolerance requirements and uniquely overcomes the limitation ofmaterials selection. Further, a plurality of subreservoirs can beassociated with a single ullage thereby making it possible toincorporate a wide variety of delivery profiles within a single device.

Another useful liquid delivery device is that described in U.S. Pat. No.5,226,896 issued to Harris. This device comprises a multidose syringehaving the same general appearance as a pen or mechanical pencil. Thedevice is specifically adapted to provide for multiple measuredinjections of materials such as insulin or human growth hormones.

Still another type of liquid delivery device is disclosed in U.S. Pat.No. 4,592,745 issued to Rex et al. This device is, in principle,constructed as a hypodermic syringe, but differs in that it enablesdispensing of a predetermined portion from the available medicine and inthat it dispenses very accurate doses.

The present invention seeks to significantly improve over the prior artby providing a novel fluid delivery device which is compact, is easy touse by ambulatory patients, and is eminently capable of meeting the moststringent of fluid delivery tolerance requirements.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus havinga self-contained stored energy membrane for expelling fluids at aprecisely controlled rate which is of a compact, extremely low profile,laminate construction. More particularly, it is an object of theinvention to provide such an apparatus which is of very low profile sothat it can conveniently be used for the precise delivery ofpharmaceutical fluids, such as insulin solution and the like, into anambulatory patient at controlled rates over extended periods of time.

It is another object of the invention to provide an apparatus of theaforementioned character which is small, compact, highly reliable andeasy-to-use by lay persons in a non-hospital environment.

It is another object of the invention to provide an apparatus asdescribed in the preceding paragraphs which, can be used for intravenousinfusion of fluids and, in a second form, can be used for subdermalinfusion of fluids. In this regard, the apparatus includes a novel andunique delivery cannula having a body portion disposed within acircuitous channel formed within the base superstructure of theapparatus and a pierceable portion which extends outwardly from the baseof the apparatus. The cannula is mounted within the circuitous channelin a manner such that the pierceable portion thereof extends generallyperpendicularly from the base for easy insertion into the patient's arm,leg or other portions of the body.

Another object of the invention is to provide an apparatus whichembodies a soft, pliable, conformable mass which defines an ullagewithin the reservoir of the device which will closely conform to theshape of the stored energy membrane thereby effectively avoidingextended flow delivery rate tail-off at the end of the fluid deliveryperiod.

A further object of the invention is to provide a low profile, fluiddelivery device of laminate construction as described in the precedingparagraph in which a centrally disposed conformable mass is free to movebetween a central chamber and a toroidal chamber formed in the cover ofthe device thereby permitting the device to meet even the most stringentfluid delivery tolerance requirements.

Another object of the invention is to provide an apparatus as describedwhich includes a dual chamber fluid reservoir that permits controlleddelivery of the same or different medicaments to the patient over timein a precisely controlled manner.

Another object of the invention is to provide an apparatus of thecharacter described which includes novel fluid rate control means forprecisely controlling the rate of fluid flow from the device.

Another object of the invention is to provide an apparatus which, due toits unique construction, can be manufactured inexpensively in largevolume by automated machinery.

Other objects of the invention are set forth in U.S. Pat. No. 5,205,820which is incorporated herein by reference and still further objects willbecome apparent from the discussion which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of the base portion of one form of the lowprofile, subdermal infusion apparatus of the invention partly brokenaway to show internal construction.

FIG. 2 is an exploded, cross-sectional view of the form of the inventionshown in FIG. 1 illustrating the base portion of the apparatussuperimposed over the barrier membrane, the distendable membrane and thecover of the apparatus.

FIG. 3 is a cross-sectional view of the apparatus of FIG. 2 shown in anassembled configuration.

FIG. 4 is an enlarged cross-sectional view taken along lines 4--4 ofFIG. 1.

FIG. 5 is an enlarged, cross-sectional view of the area designated as 5in FIG. 3.

FIG. 6 is a top plan view of the base portion of another form of the lowprofile infusion apparatus of the invention partly broken away to showinternal construction.

FIG. 7 is a generally perspective view of the cannula and septumassembly of this latest form of the invention.

FIG. 8 is an exploded, cross-sectional view of the form of the inventionshown in FIG. 6 illustrating the base portion of the apparatussuperimposed over the rate control element, the distendable membrane,and the cover of the apparatus.

FIG. 9 is a cross-sectional view of the apparatus of FIG. 8 shown in anassembled configuration.

FIG. 10 is an enlarged, fragmentary cross-sectional view similar to FIG.9 but showing fluid being expelled from the fluid reservoir of thedevice.

FIG. 11 is a top plan view of the base portion of still another form ofthe low profile infusion apparatus of the invention partly broken awayto show internal construction.

FIG. 12 is an exploded, cross-sectional view of the form of theinvention shown in FIG. 11 illustrating the base portion of theapparatus superimposed over the rate control device, the distendablemembrane, and the cover of the apparatus.

FIG. 13 is an enlarged, cross-sectional view taken along lines 13--13 ofFIG. 11.

FIG. 14 is an enlarged fragmentary, cross-sectional view of the centralportion of the device.

FIG. 15 is a fragmentary, cross-sectional view similar to FIG. 14, butshowing fluid being expelled from the fluid reservoir of the device.

FIG. 16 is an enlarged, generally perspective view of one of the fillingsubassemblies of the form of the invention shown in FIGS. 11 through 13.

FIG. 17 is an enlarged, generally perspective view of cannula assemblyof the apparatus of the invention shown in FIGS. 11 and 12.

FIG. 18 is a top plan view of the base portion of yet another form ofthe low profile infusion apparatus of the invention partly broken awayto show internal construction.

FIG. 19 is a generally perspective view of the cannula, septum assembly,and fluid outlet assembly of the latest form of the invention.

FIG. 20 is an enlarged, cross-sectional view taken along lines 20--20 ofFIG. 18.

FIG. 21 is an exploded, cross-sectional view of the form of theinvention shown in FIG. 18 illustrating the base portion of theapparatus superimpossed over the rate control device, barrier member,the distendable membrane, and the cover of the apparatus.

FIG. 22 is a generally enlarged, fragmentary, cross-sectional view ofthe septum assembly of the invention shown in FIG. 21.

FIG. 23 is a greatly enlarged, fragmentary, cross-sectional view of analternate form of the septum assembly.

FIG. 24 is an enlarged, cross-sectional view of the apparatus of FIG. 21shown in an assembled configuration.

FIG. 25 is a cross-sectional view similar to FIG. 24, but showing fluidbeing expelled from the fluid reservoir of the device.

FIG. 26 is a top plan view of the base portion of yet another form ofthe low profile infusion apparatus of the invention partly broken awayto show internal construction.

FIG. 27 is a generally perspective view of the cannula of this latestform of the invention.

FIG. 28 is an enlarged view taken along lines 28--28 of FIG. 26.

FIG. 29 is an exploded cross-sectional view of the form of the inventionshown in FIG. 26 illustrating the base portion of the apparatussuperimpossed over the rate control device, the first barrier membrane,a second barrier membrane, the distendable membrane, and the cover ofthe apparatus.

FIG. 30 is an enlarged, generally perspective, exploded view of thefluid outlet subassembly of this latest form of the invention.

FIG. 31 is an enlarged, cross-sectional view taken along lines 31--31 ofFIG. 26.

FIG. 32 is an enlarged, cross-sectional view similar to FIG. 31, butshowing fluid being expelled from the fluid reservoir of the device.

DESCRIPTION OF THE INVENTION

Referring to the drawings and particularly to FIGS. 1 through 5, oneform of the ultra low profile, expandable ullage fluid delivery deviceof the invention is there shown and generally designated by the numeral30. As best seen in FIG. 3 this embodiment of the invention comprises afluid reservoir 32 disposed within a central chamber 34 formed in acover 35. Also disposed within central chamber 34 is a centralconformable ullage, or first conformable mass 36 which is in an inferiorposition to central fluid reservoir 32 as the device is shown in FIG. 3.Cover 35 also includes a generally toroidal-shaped chamber 92 withinwhich a generally toroidal-shaped second conformable mass or ullage 38is disposed so that it circumscribes first mass 36.

The apparatus of the form of the invention shown in FIGS. 1 through 4also comprises a base 40 having a first surface 42 which has a centralportion 42a and a peripheral portion 42b circumscribing central portion42a (FIG. 2). Peripheral portion 42b is provided with acircumferentially extending, concave surface 43a which defines agenerally toroidal-shaped expansion channel or groove 43 formed withinbase 40. Base 40 is also provided with a second surface 44 to which anadhesive pad assembly 46 is affixed. After a peal strip 46a is removedfrom the pad assembly to expose an adhesive "A", the device can beaffixed to the patient's body. Formed within base 40 is a circuitouschannel 50 (FIG. 1), which receives a portion of the infusion means, orserpentine-shaped hollow cannula 52, of the invention.

The apparatus of this initial form of the invention also includes auniquely configured stored energy means for forming, in conjunction withthe central portion 42a of the base, the fluid reservoir 32. Fluidreservoir 32 has an inlet port 56 and an outlet port 60. Inlet port 56is in communication with an outlet port 62a which is provided in anenlarged diameter portion 62 of cannula 52. Filling of fluid reservoir32 is accomplished via a septum assembly 63 having a pierceable septum63a (FIG. 5). A flow control means is also provided which here comprisesthe microbore portion 52a of the cannula which causes the fluid flowinginto the enlarged diameter portion of the cannula via septum assembly 63to flow through port 62a and toward reservoir 32.

The stored energy means is here provided in the form of a generallyplanar distendable membrane 70 which overlays surface 42 of the base.Membrane 70 includes an inner O-ring like protuberance 70a and aradially spaced, outer O-ring like protuberance 70b. These O-ring likeprotuberances form a part of the sealing means of the invention forsealably interconnecting base 40 and cover 35 and are sealably receivedwithin generally circular-shaped, radially spaced inner and outer O-ringgrooves 72a and 72b formed in surface 42 of base 40 (see FIGS. 1 and 7).Grooves 72a and 72b also form a part of the sealing means of theinvention. When the apparatus is assembled in the manner shown in FIG.3, membrane 70 spans central portion 42a as well as thecircumferentially extending grooved outer portion 42b of base 40. Theinner and outer O-ring like protuberances are also sealably receivablewithin O-ring grooves 73a and 73b which are formed in cover 35 and whichalso comprise a part of the sealing means of the invention. Materialssuitable for use in constructing the base, the cover and the distendablemembrane are discussed in detail in U.S. Pat. No. 5,205,820 which isincorporated herein by reference.

Disposed within a generally circular shaped recess 75 formed in base 40is a barrier or separation membrane 77 which prevents fluid within fluidchamber 32 from contacting distendable membrane 70. Membrane 77 can beformed from any suitable elastomeric material such as polyurethane,silicon or synthetic rubber.

With the construction shown in FIG. 3, the central or first conformablemass 36 of the ullage defining means is disposed within chamber 34 forengagement with membrane 70 which, after being distended, will tend toreturn to its less distended configuration. It is to be noted that bothof the conformable masses 36 and 38 are uniquely covered by distendablemembrane 70 and both continuously vary in shape as the distendablemembrane distends outwardly from the base (FIG. 3).

A unique feature of this latest embodiment of the invention resides inthe fact that the first conformable mass 36 communicates with thesecond, outer toroidal-shaped mass 38 via a plurality of passageways 78which interconnect the first central chamber 34 formed in cover 35 withthe second toroidal-shaped chamber 92 formed in cover 35 (FIG. 3).Conformable masses 36 and 38 preferably comprise a deformable, flowablemass constructed from a suitable gel material. Accordingly, in a mannerpresently to be described, the gel which makes up first conformable mass36 can expand into chamber 92 formed in cover 35 via passageways 78 asthe distendable membrane 70 distends outwardly during filling of fluidchamber 32.

Turning particularly to FIGS. 1, 2, and 3, the serpentine-shaped cannula52 of the device includes the previously identified enlarged diameterportion 62 and the microbore portion 52a which terminates in aneedle-like outboard extremity 52b. As best seen in FIG. 4, the enlargeddiameter portion 62 of the cannula is held in position within channel 50by a potting compound "P" of a character well known to those skilled inthe art.

Turning particularly to FIG. 2, it can be seen that cover 35 is providedwith an upstanding protuberance 83 which permits joining of the cover 35to the base 40 by a sonic welding technique of a character understood bythose skilled in the art. Prior to joining the cover and the base and,prior to positioning the distendable membrane over the cover, chambers34 and 92 are filled with gel. Also, barrier membrane 77 is, at thistime, be appropriately bonded to the base along its periphery byadhesive bonding or like techniques. When the cover and base aresealably joined together, the O-ring portions 70a and 70b are guidedinto sealable engagement with grooves 72a and 72b respectively so as toseal distendable membrane 70 relative to the base. If desired, asuitable adhesive can be placed within grooves 72a and 72b to bond theO-ring-like portions 70a and 70b to the base to enhance sealing. Afterthe cover and base have been interconnected, conformable ullages 36 and38 are sealably captured between distendable membrane 70 and the innersurfaces of cover 35 which define chambers 34 and 92.

Following the interconnection of base 40 with cover 35 in the mannerdescribed in the preceding paragraphs, fluid reservoir 32 can be filledvia septum assembly 63 using a suitable syringe assembly containing thebeneficial agent to be delivered to the patient. As the fluid chamberfills, conformable mass 36 will conform to the central portion of thedistendable membrane in the manner shown in FIG. 3 causing the gel whichcomprises mass 36 to be forced inwardly and to overflow into the secondtoroidal-shaped chamber 92 via passageways 78. As the gel flows underpressure into chamber 92, the outer peripheral portion 70c ofdistendable membrane 70 will deform toward concave surface 43a and intobase channel 43 permitting this channel to, at least, partially fillwith gel. As the peripheral portion 70c of the distendable membrane 70distends into channel 43, any gases contained therein will be vented toatmosphere via vent means which here comprises a passageway 40d and avent plug 79 (see FIG. 3). With this novel construction, elevated fluidpressures within the fluid chamber 32 can readily be accommodatedwithout having to increase the height of the chamber and, therefore, theoverall height of the device. During the fluid expelling step, the gelcan, of course, flow in the opposite direction from toroidal-shapedchamber 92 into first or central chamber 34 so as to conform todistendable membrane 70 as it tends to return toward its less distendedconfiguration.

With chambers 34 and 92 filled with gel and with fluid reservoir 32filled with the selected beneficial agent to be delivered to thepatient, the device can be safely stored until time of use. At time ofuse, the novel needle protection means, or protective cover 85 can bebroken away from base 40 along serration 87 (FIG. 3) and removed fromthe cannula thereby permitting fluid to flow outwardly of cannula end52b.

Referring now to FIGS. 6 through 10, another form of the ultra lowprofile infusion device of the invention is there shown and generallydesignated by the numeral 100. This latest embodiment of the inventionis similar in many respects to the embodiment shown in FIGS. 1 through 5and like numbers are used to identify like components. This latestembodiment of the invention comprises a single fluid reservoir 102 (FIG.9) disposed within a first central chamber 34 formed in a cover 35 whichis identical to that previously described and includes conformablemasses or ullages 36 and 38 of the character previously described whichare in communication via passageways 78.

As best seen in FIGS. 8 and 9, base 106 of this embodiment is of aslightly different construction having a central, generally convexsurface 106a and a peripheral portion 106b which includes a concavesurface 110a which defines a generally toroidal-shaped expansion channelor groove 110 formed within base 106. In this latest form of theinvention, convex portion 106a, in cooperation with conformable masses36 and 38, comprises the ullage means of the invention. As before, base106 has a surface 106c to which an adhesive pad assembly 112 is affixed.Integrally molded within base 106 is a serpentine-shaped hollow cannula114, which comprises a part of the infusion means of this form of theinvention.

The apparatus shown in FIGS. 6 through 9 includes a uniquely configuredstored energy means identical to that described in connection with theembodiment shown in FIGS. 1 through 5 and forms, in conjunction with thecentral portion 106a of the base, the fluid reservoir 102. Fluidreservoir 102 has an inlet port 116 and an outlet port 120. Inlet port116 is in communication with an outlet port 114a which is provided in anenlarged diameter portion 114b of cannula 114. Filling of fluidreservoir 102 is accomplished via a septum assembly 63 of the characterpreviously described having a septum 63a.

In this latest form of the invention, flow control means comprises botha uniquely shaped hydrogel rate control device 118 as well as the microbore portion 114c of the cannula. Rate control device 118 is held inplace within a recess 121 formed in base 106 by any suitable means suchas adhesive bonding (FIG. 8). In use, the hydrogel rate control deviceswells upon imbibing fluid and functions to precisely control the rateof fluid flow from reservoir 102.

As in the earlier described form of the invention, the stored energymeans or membrane 70, overlays the base and includes an inner O-ringlike protuberance 70a and a radially spaced, outer O-ring likeprotuberance 70b. These O-ring like protuberances, which form a part ofthe sealing means, are sealably received within generallycircular-shaped, radially spaced inner and outer O-ring grooves 122a and122b formed in base 106 (see FIGS. 8 and 9). As before, grooves 122a and122b also form a part of the sealing means of the invention. When theapparatus is assembled in the manner shown in FIG. 9, membrane 70 spansthe central portion of the base as well as the circumferentiallyextending grooved outer portion 106b. The inner and outer O-ring likeprotuberances are also sealably receivable within O-ring grooves 73a and73b which are formed in cover 35 (FIG. 8) and which comprise a part ofthe sealing means.

In the construction shown in FIG. 9, the central concave portion 106a ofthe base forms the rigid ullage portion of the ullage means and ullageportions 36 and 38 form the conformable ullage portions of the ullagemeans. As before, the conformable ullage portions of the ullage meansare covered by distendable membrane 70 and both continuously vary inshape as the distendable membrane distends outwardly from the base asfluid is introduced into reservoir 102 via the septum assembly. Onceagain, central conformable ullage 36 communicates with the outertoroidal ullage 38 via passageways 78 so that, as fluid chamber 102 isfilled, the gel which makes up the central ullage is engaged by membrane70 urging it outward and causing it to flow into chamber 92 of cover 35.This causes the gel contained within this chamber to, in turn, expand,along with membrane 70, into channel 110 formed in base 106 in themanner shown in FIG. 9.

Turning particularly to FIGS. 6 and 8, the serpentine-shaped cannula 114of the device there illustrated includes the previously identifiedenlarged diameter portion 114b and the microbore portion 114c whichterminates in a needle-like outboard extremity 114d. Cannula 114 ismolded in place with a base 106 in a manner well known by those skilledin the art. Extremity 114d is protected by a protective cover 85a whichis similar to the previously discussed cover 85. However, cover 85aincludes an outer sheath 85b which is connected to base 106 along aserration line 87. Sheath 85b telescopically receives a removable plug85c which closely surrounds extremity 114d of the cannula.

Prior to joining the cover and the base as by sonic welding and, priorto positioning the distendable membrane over the cover, chambers 34 and92 are filled with gel. Also, rate control device 118 is, at this time,emplaced into cavity 121. When the cover and base are sealably joinedtogether, the O-ring protuberances or portions 70a and 70b are guidedinto sealable engagement with grooves 73a and 73b respectively so as toseal distendable membrane 70 relative to the base. If desired, asuitable adhesive can be placed within grooves 73a and 73b to bond theO-ring-like protuberance 70a and 70b to the base to enhance sealing.After the cover and base have been interconnected, conformable ullages36 and 38 are sealably captured between distendable membrane 70 and theinner surfaces of cover 35 which define chambers 34 and 92.

Following the interconnection of base 106 with cover 35 in the mannerdescribed in the preceding paragraphs, fluid reservoir 102 can be filledvia septum assembly 63 using a suitable syringe assembly containing thebeneficial agent to be delivered to the patient. Filter means, shownhere as a porous filter 123, directs and filters the fluid flowing outof outlet 114a. Filter 123 can be constructed from any suitable porousmaterial such as a polycarbonate material. As the fluid chamber fills,the peripheral portion 70c of the distendable membrane 70 will distendinto channel 110, and any gases contained therein will be vented toatmosphere via passageway 125 and vent plug 127 (see FIG. 9). During thefluid expelling step, the gel can, of course, flow in the oppositedirection from toroidal chamber 92 into central chamber 34 so as toconform to distendable membrane 70 as it tends to return toward its lessdistended configuration.

Turning next to FIGS. 11 through 17, still another form of the ultra lowprofile infusion device of the invention is there shown and generallydesignated by the numeral 150. This latest embodiment of the inventionis somewhat similar to the embodiment shown in FIGS. 6 through 10 andlike numbers are used to identify like components. This latestembodiment of the invention uniquely comprises a dual chamber fluidreservoir 152 (FIG. 13) which extends into a central chamber 156a formedin a cover 156. Central chamber 156a is here slightly larger thanchamber 34 of the previously described embodiment so as to accommodatethe dual chamber fluid reservoir. As before, cover 156 includes aplurality of conformable ullages of the character previously describedwhich are in communication via passageways 157.

As best seen in FIGS. 11 and 13, base 160 of this embodiment is of aslightly different construction having first and second filling meansfor separately filling the dual reservoirs 152a, and 152b. Like theearlier described embodiment, base 160 has a central, surface 160a and aperipheral portion 160b which includes a generally toroidal-shapedexpansion channel or groove 162 formed within base 160 and defined byconcave surface 162a. In this latest form of the invention, portion 160ais generally planar in shape. Base 160 also has a surface 160c to whichan adhesive pad assembly 164 is affixed. Integrally molded within base160 is a uniquely-shaped hollow cannula 166 (FIG. 17), which comprises apart of the infusion means of this form of the invention.

The apparatus shown in FIGS. 11 through 14 includes a uniquelyconfigured stored energy means very similar to that previously describedand, in conjunction with the central portion 160a of the base, forms thetwo fluid reservoirs 152a and 152b. As best seen in FIGS. 11, 13, and14, fluid reservoir 152a has an inlet port 168 and an outlet port 170.Similarly, fluid reservoir 152b has an inlet port 172 and an outlet port174. Outlet ports 170 and 174 communicate with inlet ports 175 and 177respectively provided in enlarged diameter portion 166a of cannula 166(FIG. 17). Filling of reservoir 152a is accomplished via a first septumassembly 180 of the character previously described, while fluidreservoir 152b is filled via septum assembly 182. As best seen in FIG.17, each of the septum assemblies communicate with an elongated tubularmember "T" which terminates at the inlets of fluid reservoirs 152a and152b.

In this latest form of the invention, flow control means are provided inthe form of first and second rate control membranes 183 and 184respectively which are disposed within cavities 183a and 184a formed inbase 160 proximate outlets 170 and 174. Membranes 183 and 184 can beconstructed from a polycarbonate material or, alternatively, can beformed from a hydrogel material of the character previously described.

As in the earlier described form of the invention, the stored energymeans or membrane 186, overlays the base and includes an inner O-ringlike protuberance 186a and a radially spaced, outer O-ring likeprotuberance 186b. These O-ring like protuberance are sealably receivedwithin generally circular-shaped, radially spaced inner and outer O-ringgrooves 187a and 187b formed in base 160 (see FIGS. 12 and 13). When theapparatus is assembled in the manner shown in FIG. 13, membrane 186spans the central portion of the base as well as the circumferentiallyextending grooved outer portions 160b. The inner and outer O-ring likeportions are also sealably receivable within O-ring grooves 189a and189b formed in cover 156 (FIG. 12).

Provided in the construction shown in FIGS. 13 and 14, is a highly novelseparation means, shown here as a yieldable barrier or separationmembrane 190. As best seen in FIG. 11, membrane 190 is bonded to thebase along the periphery "P" thereof and along a central dividing line"L" that divides the membrane into first and second portions 190a and190b. More particularly, the membrane is bonded to the base along thebond areas designated as 191. Areas 191 circumscribes central portion160a while area 191b bisects the central portions. With this novelconstruction, as fluid under pressure is introduced into the device viathe first and second filling means enters both the stored energymembrane 186 and the separation membrane 190 will deform outwardly inthe manner shown in FIG. 13 to form the two fluid reservoirs. As before,the ullage means are covered by distendable membrane 186 and bothcontinuously vary in shape as the distendable membrane distendsoutwardly from the base as fluid is introduced into reservoirs 152a and152b via septum assemblies 180 and 182. Once again, the centralconformable ullage 194 communicates with the outer toroidal ullage 195via passageways 157 so that, as fluid chambers 152a and 152b are filled,the gel which makes up the central ullage contained within centralchamber 156a is engaged by membrane 186 urging it outward and causing itto flow into toroidal chamber 156b of cover 156. This causes the gelcontained within this chamber, along with membrane 186 to, in turn,expand into channel 162 formed in base 160 in the manner shown in FIG.13. As before, gases contained in this channel will be vented viapassageway 125 and vent plug 127. As the fluid is expelled from thereservoirs, the gel will return to central chamber 156a in the mannershown in FIG. 15.

Turning particularly to FIGS. 14 and 17, the uniquely-shaped cannula 166of the device there illustrated includes the previously identifiedenlarged diameter portion 166a and the smaller diameter portion 166bwhich terminates in a needle-like outboard extremity 166c. Cannula 166is molded in place with a base 160 in a manner well known by thoseskilled in the art.

Prior to joining the cover and the base as by adhesive bonding or sonicwelding and, prior to positioning the distendable membrane over thecover, chambers 156a and 156b are filled with gel. Also, rate controlmembranes 183 and 184 are, at this time, emplaced into cavities 183a and184b and separation membrane 190 is adhesively bonded to base 160 alongbond areas 191a and 191b. When the cover and base are sealably joinedtogether, the O-ring protuberances 186a and 186b are guided intosealable engagement with grooves 187a and 187b respectively so as toseal distendable membrane 186 relative to the base. If desired, asuitable adhesive can be placed within the grooves to bond theO-ring-like protuberances to the base and to the cover to enhancesealing. After the cover and base have been interconnected, conformableullages 194 and 195 are sealably captured between distendable membrane186 and the inner surfaces of cover 156 which define chambers 156a and156b.

Following the interconnection of base 160 with cover 156 in the mannerdescribed in the preceding paragraphs, fluid reservoir 152a can befilled via septum assembly 180 using a suitable syringe assemblycontaining the beneficial agent to be delivered to the patient. As thefluid is introduced via septum assembly 180 and tube "T", it willimpinge upon portion 190a of membrane 190 causing it, along with aportion of distendable membrane 186, to distend outwardly to formreservoir 152a. In similar fashion, fluid reservoir 152b can be filledvia septum assembly 182. Once again, as fluid is introduced into thedevice via septum assembly 182, and tube "T", it will impinge uponportion 190b of membrane 190 causing it, along with a portion ofdistendable membrane 186, to distend outwardly to form reservoir 152b.As the central portion of the distendable membrane 186 thusly extendsoutwardly, the peripheral portion thereof will extend into channel 162in the manner shown in FIG. 13. Fluid flowing into reservoirs 152a and152b will be filtered by filter means shown here as porous filters "F"which are carried within tubes "T".

As fluid is dispelled from reservoirs 152a and 152b in the manner shownin FIG. 15, the central portion of the distendable membrane will movetoward the central portion of the base causing fluid to flow into inletports 175 and 177 of the cannula via rate controls 183 and 184. At thesame time, the peripheral portion of the distendable membrane will causeconformable mass 195 to flow toward central chamber 156a in the mannershown in FIG. 15.

It will be appreciated that reservoirs 152 and 152b can be filled withthe same or different fluids. Further, the rate flow of the fluids fromthe two reservoirs can be precisely regulated as desired by properselection of the rate control means or member 183 and 184.

Turning next to FIGS. 18 through 25, another form of the ultra lowprofile infusion device of the present invention is there shown andgenerally designated by the numeral 200. This latest embodiment of theinvention is similar in some respects to the embodiment shown in FIGS. 1through 5, but comprises a sealing means of different construction forsealably interconnecting the distendable membrane with the base and withthe cover. This latest form of the invention also comprises a singlefluid reservoir 202 disposed within a central chamber 204 formed in acover 205 and includes a plurality of conformable ullages which are incommunication (FIG. 21). More particularly, the device includes acentral conformable ullage defining means, or first conformable mass 206which is in an inferior position to central fluid reservoir 202, asviewed in FIG. 24, and a toroidal-shaped, conformable ullage definingmass, or second conformable mass 208 circumscribing ullage 206.

As best seen in FIGS. 21 and 24, the apparatus here comprises a base 210having a first surface 212, including a central portion 212a and aperipheral portion 212b circumscribing central portion 212a. Peripheralportion 212b includes a concave surface 213a which defines a generallytoroidal-shaped expansion channel or groove 213 formed within base 210.As before, base 210 is also provided with a second surface 214 to whichan adhesive pad assembly 216 is affixed. After a peal strip is removedfrom the pad assembly to expose a thin adhesive layer "A", the devicecan be conveniently affixed to the patient's body. Formed within base210 is a bore 220 (FIG. 18), which receives a portion of the infusionmeans, or hollow cannula 222, of the invention.

The apparatus shown in FIGS. 18 through 25 also includes a stored energymeans for forming, in conjunction with the central portion of the base,the fluid reservoir 202. Fluid reservoir 202 has an inlet port 226 andan outlet port 230. Inlet port 226 is in communication with an outletport 232 which is provided in an enlarged diameter portion 222a ofcannula 222 (FIG. 19). Filling of fluid reservoir 202 is accomplishedvia a septum assembly 236 of the character previously described having apierceable septum 236a (FIG. 22). As before, a flow control meanscomprises the micro bore portion 222b of the cannula. The flow controlmeans in this latest embodiment of the invention also comprises a flowcontrol member 238, the character of which will presently be described.

The stored energy means is here provided in the form of a generallyplanar distendable membrane 240 which overlays surface 212 of the base.When the apparatus is assembled in the manner shown in FIG. 24, membrane240 spans central portion 212a as well as the circumferentiallyextending channeled outer portion 212b of base 210. Membrane 240 issealably receivable within inner and outer ring-like grooves 243 and 245which are formed in cover 205 (FIG. 21). Grooves 243 and 245 form a partof the sealing means of this embodiment of the invention as do inner andouter ring-like protuberances 247 and 249 formed on base 210. As bestseen by referring to FIG. 24, when base 210 and cover 205 are joinedtogether, protuberance 247 is closely received within groove 243 andprotuberance 249 is closely received within groove 245 in a manner tosealably clamp inner and outer ring-like portions 240a and 240b ofdistendable membrane 240 between base 210 and cover 205.

Disposed within a generally circular shaped recess 254 formed in base210 is a barrier means or barrier membrane 256 which prevents fluidwithin fluid reservoir 202 from contacting distendable membrane 240.Membrane 256 can be formed from any suitable elastomeric material suchas polyurethane, silicon or synthetic rubber.

With the construction shown in FIG. 24, the central or first conformablemass 206 of the ullage defining means is disposed within chamber 204 forengagement with membrane 240 which, after being distended, will tend toreturn to its less distended configuration. As was the case with thepreviously discussed embodiments, the ullage defining means of thislatest embodiment of the invention comprises not only the centralconformable ullage 206, but also the outer toroidal shaped, conformableullage 208. Both of the conformable masses 206 and 208 are uniquelycovered by distendable membrane 240 and both continuously vary in shapeas the distendable membrane distends outwardly from the base (FIG. 24).

As before in this latest embodiment of the invention first conformablemass ullage 206 communicates with the second outer toroidal-shaped mass208 via passageways 261 which interconnect the first or central chamber204 formed in cover 205 with the second toroidal-shaped chamber 264formed in cover 205 (FIG. 21). As before, conformable masses 206 and 208preferably comprise a deformable, flowable mass constructed from asuitable gel material. Accordingly, in a manner presently to bedescribed, the gel which makes up first conformable mass 206 can expandinto chamber 264 formed in cover 205 via passageways 261 as thedistendable membrane 240 distends outwardly during filling of fluidchamber 202.

Turning particularly to FIGS. 18, 19, and 24, the generally straightcannula 222 of the device includes the previously identified enlargeddiameter portion 222a and the microbore portion 222b which terminates inan outboard extremity 222c which is suitably interconnected with a luerconnector 265. In this latest form of the invention, the cannula ismolded in place within bore 220.

Turning particularly to FIG. 21, it can be seen that, as before, cover205 is provided with an upstanding protuberance 267 which permitsjoining of the cover 205 to the base 210 by a sonic welding technique ofthe character previously described. Prior to joining the cover and thebase and, prior to positioning the distendable membrane over the cover,chambers 204 and 264 are filled with gel. Also barrier membrane 256 is,at this time, appropriately bonded to the base by adhesive bonding orlike techniques well known to those skilled in the art. When the coverand base are sealably joined together, the ring-like protuberances 247and 249 are guided into grooves 243 and 245 respectively so as tosealably clamp distendable membrane 240 securely between the base andthe cover. If desired, a suitable adhesive can be placed within grooves243 and 245 to bond portions 240a and 240b of the distendable membraneto the cover to enhance sealing. After the cover and base have beeninterconnected, conformable ullages 206 and 208 are sealably capturedbetween distendable membrane 240 and the inner surfaces of cover 205which define chambers 204 and 264. It is to be noted that chambers 204and 256 can also be filled with gel via a fill port 205f and apassageway 205p (see FIG. 24).

Following the interconnection of base 210 with cover 205 in the mannerdescribed in the preceding paragraphs, fluid reservoir 202 can be filledvia septum assembly 236 using a suitable syringe assembly containing thebeneficial agent to be delivered to the patient. As the fluid chamberfills, conformable mass 206 will conform to the central portion of thedistendable membrane in the manner shown in FIG. 24 causing the gelwhich comprises mass 206 to be forced inwardly and to overflow into thesecond toroidal-shaped chamber 264 via passageways 261. As the gel flowsunder pressure into chamber 264, the outer peripheral portion of thedistendable membrane 240 will deform toward concave surface 213a andinto base channel 213 permitting this channel to, at least, partiallyfill with gel. As the peripheral portion of the distendable membranedistends into channel 213, any gases contained therein will be vented toatmosphere via vent means which here comprises a passageway 269 and avent plug 271 (see FIGS. 18 and 20).

During the fluid expelling step, the gel can, of course, flow in theopposite direction from toroidal-shaped chamber 264 into first orcentral chamber 204 so as to conform to distendable membrane 240 as ittends to return toward its less distended configuration.

With chambers 204 and 264 filled with gel, with fluid reservoir 202filled with the selected beneficial agent to be delivered to the patientand with the luer connector 265 connected to a valved administrationline, the device can be safely stored until time of use. At time of use,the administration line can be opened to fluid flow toward the patient.

Turning to FIG. 23 a slightly different form of cannula and septum isthere illustrated. Here the fill end of cannula 223 is bell shaped tosealably receive a matching shaped septum 237a. This alternate design isbetter suited for certain end applications of the device.

Referring now to FIGS. 26 through 32, still another form of the ultralow profile infusion device of the invention is there shown andgenerally designated by the numeral 300. This latest embodiment of theinvention is similar in many respects to the embodiment shown in FIGS.18 through 25 and like numbers are used to identify like components.This latest embodiment of the invention comprises a single fluidreservoir 302 (FIG. 31) disposed within a first central chamber 204formed in a cover 205 which is identical to that previously described inconnection with the embodiment of FIGS. 18 through 25 and includesconformable masses 206 and 208 of the character previously describedwhich are in communication via passageways 261.

As best seen in FIGS. 29 and 31, base 306 of this embodiment is of aslightly different construction having a central, generally convexsurface 306a and a peripheral portion 306b which includes a concavesurface 310a which defines a generally toroidal-shaped expansion channelor groove 310 formed within base 306. In this latest form of theinvention, convex portion 306a, in cooperation with the conformablemasses 206 and 208, comprise the ullage means of the invention. Asbefore, base 306 has a surface 306c to which an adhesive pad assembly216 is affixed. Integrally molded within base 306 is a hollow cannula314, which comprises a part of the infusion means of this form of theinvention.

The apparatus shown in FIGS. 26 through 32 includes a uniquelyconfigured stored energy means identical to that described in connectionwith the embodiment shown in FIGS. 18 through 25 and forms, inconjunction with the central portion 306a of the base, the fluidreservoir 302. Fluid reservoir 302 has an inlet port 316 and an outletport 320. Inlet port 316 is in communication with an outlet port 314awhich is provided in an enlarged diameter portion 314b of cannula 314.Filling of fluid reservoir 302 is accomplished via a septum assembly 236of the character previously described having a septum 236a.

In this latest form of the invention, flow control means comprises botha uniquely shaped hydrogel rate control device 318 as well as the microbore portion 314c of the cannula. Rate control device 318 is held inplace within a recess 321 formed in base 306 by any suitable means suchas adhesive bonding. In use, the hydrogel rate control device swellsupon imbibing fluid and functions to precisely control the rate of fluidflow from reservoir 302.

As in the earlier described form of the invention, the stored energymeans or membrane 240, overlays the base and is sealably interconnectedwith cover 205 in the same manner as described in connection with theform of the invention shown in FIGS. 18 through 25. When the apparatusis assembled in the manner shown in FIG. 31, membrane 240 spans thecentral portion of the base as well as the circumferentially extendingchanneled outer portion 306b. Inner and outer ring-like protuberances323 and 325 are sealably receivable within ring-like grooves 243 and 245which are formed in cover 205 (FIG. 31) and which comprise a part of thesealing means of the invention.

In the construction shown in FIG. 31, the central convex portion 306a ofthe base forms the rigid ullage portion of the ullage means and ullageportions 206 and 208 form the conformable ullage portions of the ullagemeans. As before, the conformable ullage portions of the ullage meansare covered by distendable membrane 240 and both continuously vary inshape as the distendable membrane distends outwardly from the base asfluid is introduced into reservoir 302 via the septum assembly. Onceagain, central conformable ullage 206 communicates with the outertoroidal ullage 208 via passageways 261 so that, as fluid chamber 302 isfilled, the gel which makes up the central ullage is engaged by abarrier membrane 328 which is disposed between distendable membrane 240and cover 205. With this construction, as reservoir 302 fills membranes240, 327, and 328 will distend outwardly in the manner shown in FIG. 31causing gel 206 to flow into chamber 264 of cover 205. This causes thegel contained within this chamber to, in turn, expand, along with themembrane 240 into channel 310 formed in base 306 in the manner shown inFIG. 31.

As before, as shown in FIG. 27, cannula 314 includes the previouslyidentified enlarged diameter portion 314b and the microbore portion 314cwhich terminates in an extremity 314d which communicates with a novelquick connect delivery assembly 331, the character of which willpresently be described.

Prior to joining the cover and the base as by sonic welding and, priorto positioning the distendable membrane 240 and the containment film 328over the cover, chambers 204 and 264 are filled with the conformablemass or gel. Containment film 328 can be constructed of variousmaterials such as cellulose acetate, polyethylene, polypropylene,polyvinyl films and the like and functions to contain the mass or gelwithin the cover. Also, rate control device 318 is, at this time,emplaced into cavity 321 and a first barrier membrane 327 is affixedalong its periphery to the central portion of base 306. When the coverand base are sealably joined together, the ring-like protuberances 323and 325 formed on base 306 are guided into sealable engagement withgrooves 243 and 245 respectively so as to sealably clamp bothdistendable membrane 240 and film 328 between the base and the cover. Ifdesired, a suitable adhesive can be placed within grooves 243 and 245 tobond to the two membranes and to the cover to enhance sealing. After thecover and base have been thusly interconnected, conformable ullages 206and 208 are sealably captured between containment film 328 and the innersurfaces of cover 205 which define chambers 204 and 264.

Following the interconnection of base 306 with cover 205 in the mannerdescribed in the preceding paragraphs, fluid reservoir 302 can be filledvia septum assembly 236 using a suitable syringe assembly containing thebeneficial agent to be delivered to the patient. Filter means, shownhere as a porous filter member 335, filters the fluid flowing out ofoutlet 314a. Filter 335 can be constructed from any suitable filtermaterial such as a polycarbonate and is backed by a fluid flow blockingmeans shown here as a blocking membrane 335a. Blocking membrane 335afunctions to direct the fluid flowing into cannula portion 314b towardfluid reservoir 302. As the fluid reservoir fills, the peripheralportions of the distendable membrane 240 and the barrier membrane 328will distend into channel 310, and any gases contained therein will bevented to atmosphere via passageway 206a and vent plug 271 (see FIG.26). During the fluid expelling step, the gel can, of course, flow inthe opposite direction from toroidal chamber 264 into central chamber204 so as to conform to barrier membrane 328 as it tends, along with thedistendable membrane, to return toward their less distendedconfiguration.

Turning particularly to FIG. 30 the novel dispensing means of the formof the invention is there illustrated. This dispensing means includesthe previously identified quick connect delivery fitting 331 having atapered extremity 331a which is telescopically and sealably receivablewithin a tapered bore 342 formed in base 306 (FIG. 29). In order toreleasably lock fitting 331 in position within bore 342 and in fluidcommunication with end 314d of cannula 314, locking means shown here asresiliently deformable locking tabs 344 are provided on base 306.Extending from the outboard end of quick connect fitting assembly 331 isan infusion set 346 having a soft cannula assembly 350, the operation ofwhich is well understood by those skilled in the art. Once the softcannula 350a has been introduced into the patient's subdermal tissue"ST" in the manner shown in FIG. 30, the cannula insertion assembly 352,which includes a trocar 352a can be removed, leaving the soft cannula350a in position within the patient. Needle cannula interconnect 354a ofthe connector assembly 354 of infusion set 346 can then be inserted intoassembly 350 and interconnect therewith using the conventional latchmechanism 355. Connector assembly 354 which forms a part of infusion set346, when connected to assembly 350, places soft cannula 350a in fluidcommunication with reservoir 302. Infusion set 346 is of a characterwell known in the art and is readily available from several commercialsources including Pharma-Plast International A/S, Lynge Denmark. Bypushing inwardly on member 334, delivery quick connect 331 can be urgedinto tapered bore 342 to a position wherein locking tabs 344 will closeabout member 344 and in engagement with a shoulder 331a formed on member331 so as to securely lock the infusion means of the invention to thebase.

Having now described the invention in detail in accordance with therequirements of the patent statutes, those skilled in this art will haveno difficulty in making changes and modifications in the individualparts or their relative assembly in order to meet specific requirementsor conditions. Such changes and modifications may be made withoutdeparting from the scope and spirit of the invention, as set forth inthe following claims.

We claim:
 1. A device for use in infusing medicinal fluid into a patientat a controlled rate comprising:(a) a base having an upper surfaceincluding a central portion and a peripheral portion circumscribing saidcentral portion, a lower surface engageable with the patient and achannel formed in said base intermediate said upper and lower surfaces,said channel having first and second ends; (b) stored energy means forforming in conjunction with said central portion of said base, areservoir having an inlet and an outlet, said stored energy meanscomprising at least one distendable membrane superimposed over saidbase, said membrane being distendable as a result of pressure impartedby fluids introduced into said reservoir to establish internal stresses,said stresses tending to move said membrane toward a less distendedconfiguration; (c) a cover connected to said base, said cover having afirst chamber and a second chamber circumscribing said first chamber andat least one passageway interconnecting said first and second chambers,said distendable membrane overlaying said first and second chamber; (d)a first conformable mass disposed within said first chamber forengagement by said distendable membrane; (e) a second conformable massdisposed within said second chamber for engagement by said distendablemembrane; (f) infusion means for infusing medicinal fluid from saidfluid reservoir into the patient, said infusion means comprising ahollow cannula having:(i) an inlet end portion disposed proximate saidchannel; (ii) a central body portion disposed within said channel formedin said base; and (iii) an end portion extending outwardly from saidchannel for insertion into the patient.
 2. A device as defined in claim1 in which said end portion of said hollow cannula extends outwardly ina direction substantially perpendicular to said lower surface of saidbase for subdermal infusion of fluid into the patient.
 3. A device asdefined in claim 1 further including flow control means in communicationwith said outlet of said reservoir for controlling the rate of fluidflow from said reservoir.
 4. A device as defined in claim 1 in which aportion of said first conformable mass is urged from said first chamberof said cover through said passageway and into said second chamber ofsaid cover as said distendable membrane is distended as a result offluids being introduced into said inlet of said reservoir.
 5. A deviceas defined in claim 1 in which said central portion of said baseincludes a convex surface.
 6. A device as defined in claim 1 furtherincluding a barrier membrane connected to said central portion of saidbase, said barrier membrane being disposed intermediate said base andsaid distendable membrane and being distendable as a result of fluidbeing introduced into said inlet of said reservoir.
 7. A device asdefined in claim 1 further including sealing means for sealablyconnecting said distendable membrane to said base and to said cover. 8.A device as defined in claim 7 in which said base and said cover eachhave first and second radially spaced sealing grooves and in which saidsealing means comprises first and second radially spaced base sealingprotuberances formed on said distendable membrane and being sealablyreceivable within said sealing grooves formed in said base and first andsecond radially spaced cover sealing protuberances formed on saiddistendable membrane and being sealably receivable within said sealinggrooves formed in said cover.
 9. An ultra low profile device for use ininfusing medicinal fluid into a patient at a controlled ratecomprising:(a) a thin base having an upper surface including a centralportion and a peripheral portion circumscribing said central portion, alower surface engageable with the patient and a generally spiral shapedchannel formed in said base intermediate said upper and lower surfacessaid channel having first and second ends; (b) stored energy means forforming in conjunction with said central portion of said base, areservoir having an inlet and an outlet, said stored energy meanscomprising at least one distendable membrane superimposed over saidbase, said membrane having a central portion and a peripheral portion,said central portion being distendable from a first configuration to asecond configuration as a result of pressure imparted by fluidsintroduced into said inlet of said reservoir to establish internalstresses, said stresses tending to move said membrane toward said firstconfiguration; (c) a cover connected to said base, said cover having afirst chamber and a second chamber circumscribing said first chamber anda plurality of passageways interconnecting said first and secondchambers; (d) a first conformable mass disposed within said firstchamber of said cover, said first conformable mass substantiallyconforming to the shape of said central portion of said distendablemembrane as said central portion moves between said first and secondconfigurations; (e) a second conformable mass disposed within saidsecond chamber of said cover for engagement by said peripheral portionof said distendable membrane; and (f) infusion means for infusingmedicinal fluid from said fluid reservoir into the patient, saidinfusion means having an inlet end disposed proximate said outlet ofsaid fluid reservoir and including a hollow cannula having:(i) a centralbody portion disposed within said generally spiral shaped channel; and(ii) an outlet end portion including a pierceable portion extendingangularly outward from said lower surface of said base for insertion into the patient.
 10. A device as defined in claim 9 further includingsealing means for sealably interconnecting said distendable membranewith said cover and said base, said sealing means comprising radiallyspaced sealing protuberances formed on said distendable membrane.
 11. Adevice as defined in claim 9 further including a yieldably deformablebarrier membrane connected to said central portion of said base, saidbarrier membrane being disposed between said central portion of saidbase and said central portion of said distendable membrane.
 12. A deviceas defined in claim 9 in which a portion of said first conformable massis urged to flow from said first chamber of said cover through saidplurality of passageways into said second chamber of said cover as saidcentral portion of said distendable membrane distends toward said secondconfiguration.
 13. A device as defined in claim 12 in which saidperipheral portion of said distendable membrane moves toward said baseas said portion of said first conformable mass flows into said secondchamber of said cover.
 14. A device as defined in claim 13 furtherincluding vent means formed in said base for venting gases from saidbase as said peripheral portion of said distendable membrane movestoward said circumferentially extending concave surface of said base.15. A device as defined in claim 13 in which said distendable membraneis bonded to said central portion of said base along the peripherythereof and along the center line thereof to define first and secondbarrier portions.